This invention relates to electrochromic devices and more particularly electrochromic devices which are useful as light controllable windows for buildings, automobiles and passenger vehicles and various types of light controllable glasses to be used for indoor decoration or partitions; display devices; and antiglare mirrors for automobiles and other vehicles.
A conventional electrochromic device such as a light controllable glass of conventional type as disclosed in Japanese Patent Laid-Open Publication No. 63-18336 is known which glass comprises a chromogenic material in the form of a film obtained by sputtering or vacuum-depositing an inorganic oxide such as tungsten oxide (WO3) over a transparent electrically conductive film.
However, the conventional film formation techniques must be carried out under vacuum, resulting in increased production costs and a requirement of a large size vacuum apparatus if an electrochromic device of a large area is intended to be produced. Furthermore, since a substrate is heated at an elevated temperature during sputtering, it is necessary to select certain conditions if a substrate other than a glass, such as a synthetic resin made substrate is used, resulting in difficulties in reducing the weight of an electrochromic device.
There is also a problem that tungsten oxide can only make an electrochromic device exhibit blue color.
An object of the present invention is to provide an electrochromic device which can be manufactured using an inexpensive color developing material with easy operations and can easily be changed in color tone.
An electrochromic device proposed by the present invention solves the above-mentioned problems of the prior art by forming an ion conductive material layer containing a specified electrochromic material.
Namely, according to the present invention, there is provided an electrochromic device comprising two conductive substrates, at least one of which is transparent, and an ion conductive substance layer disposed therebetween and containing an electrochromic substance represented by the formula 
wherein Xxe2x88x92 and Yxe2x88x92 may be the same or different and are each a counter anion selected from the group consisting of a halogen anion, ClO4xe2x88x92, BF4xe2x88x92, PF4xe2x88x92, CH3COOxe2x88x92 and CH3(C6H4)SO3xe2x88x92 and R1 and R2 may be the same or different and are each a hydrocarbon group having from 1 to 20 carbon atoms.
In the present invention, two electrically conductive substrates, at least one of which is transparent, are used. The term xe2x80x9celectrically conductive substratexe2x80x9d designates substrates which have a function as an electrode. Therefore, the conductive substrates used in the invention encompass those entirely formed from an electrically conductive material or formed with a non-electrically conductive substrate and an electrode layer disposed thereon. Regardless of whether a substrate is electrically conductive or not, it necessarily has a smooth surface at normal temperature but may have a flat or curved surface and may be deformable under stress.
At least of one of the two electrically conductive substrates is a transparent electrically conductive substrate and the other may be a transparent or opaque or reflective electrically conductive substrate.
Two conductive substrates both of which are transparent are suitable for a display device and a light controllable glass. A combination of a transparent conductive substrate and an opaque conductive substrate is suitable for a display device, while a combination of a transparent conductive substrate and a reflective substrate is suitable for an electrochromic mirror.
The transparent conductive substrate is generally formed by laminating a transparent electrode layer over a transparent substrate. The term xe2x80x9ctransparencyxe2x80x9d used herein designates an optical transmission ranging from 10 to 100 percent.
The opaque conductive substrate is may be a laminate obtained by laminating an electrode layer over one surface of a metal plate or a non-conductive opaque substrate such as various opaque plastics, ceramics, glasses, woods and stones.
The reflective electrically conductive substrate may be exemplified by (1) a laminate comprising a non-conductive transparent or opaque substrate and a reflective electrode layer formed thereon, (2) a laminate comprising a no-conductive transparent substrate having a transparent electrode layer on one of its surfaces and a reflective electrode layer on the other surface, (3) a laminate comprising a non-conductive transparent substrate having a reflective layer formed thereon and further a transparent electrode layer formed thereon, (4) a laminate comprising a reflective substrate and a transparent electrode layer formed thereon and (5) a plate-like substrate which itself functions as a reflective layer and an electrode.
No particular limitations is imposed on the transparent substrate which may thus be a color or colorless glass, a reinforced glass and a resin of color or colorless transparency. Specific examples of such a resin include polyethylene terephthalate, polyamide, polysulfone, polyether sulfone, polyether etherketone, polyphenylene sulfide, polycarbonate, polyimide, polymethyl methacrylate and polystyrene.
The substrates used in the present invention must have a smooth surface at normal temperature.
There is no particular restriction to the transparent electrode layer as long as it meets the requirements for achieving the purpose of the present invention. Specific examples of the electrode layer include electrically conductive film such as thin films of metals such as gold, silver, chrome, copper and tungsten or metal oxides such as ITO (In2O3xe2x80x94SnO2), tin oxide, silver oxide, zinc oxide and vanadium oxide.
The electrode has a film thickness in the range of usually 100 to 5,000 and preferably 500 to 3,000 angstrom. The surface resistance of the electrode is usually in the range of 0.5-500 and preferably 1-50 xcexa9/sq.
No particular limitation is imposed on a method of forming the electrode layer. Any suitable conventional methods may be employed, depending upon the metal and metal oxide constituting the electrode. In general, the formation of the electrode layer is carried out by vacuum evaporation, ion plating, sputtering and a sol-gel method. The thickness of the electrode layer is selected within the range such that the transparency thereof is not affected. The electrode layer may be partially provided with an opaque electrode-activator for the purpose of imparting oxidation-reduction capability, electric conductivity and electric double layer capacitance, the electrode-activator being provided in an amount such that the transparency of the entire electrode layer is not harmed. Electrode activators eligible for the purpose of the invention are a metal such as copper, silver, gold, platinum, iron, tungsten, titanium and lithium, an organic material having oxidation-reduction capability such as polyaniline, polythiophen, polypyrrole and phthalocyanine, a carbon material such as active carbon and graphite and a metal oxide such as V2O5, MnO2, NiO and Ir2O3 and mixtures thereof. A variety of resins may be used for integrating the electrode activator in the electrode. The opaque electrode activator may applied onto an electrode by forming on an ITO transparent electrode a composition comprising an active carbon fiber, graphite and an acrylic resin into a micro pattern in the shape of stripes or by forming on a thin-film of gold a composition comprising V2O5, acetylene black and butyl rubber in the shape of a mesh.
No particular limitation is imposed on the reflective electrode layer as long as it is stable electrochemically and has a specular surface. Eligible for the reflective electrode layer includes the films of metal such as gold, platinum, tungsten., tantalum, rhenium, osmium, iridium, silver, nickel and palladium and the film of an alloy such as platinum-palladium, platinum-rhodium and stainless steel. The reflective electrode layer is necessarily disposed onto a substrate or a transparent substrate with the reflectiveness and specularity of the layer maintained. The reflective electrode layer is formed onto a substrate by any suitable conventional method such as vacuum deposition, ion-plating and sputtering.
No particular limitation is imposed on a substrate on which the reflective electrode layer is disposed. The substrate may be transparent or opaque. Specific examples of the substrate include those as exemplified with respect to the transparent substrate described above, a variety of plastics, resins, glasses, woods and stones.
No particular limitation is imposed on materials for the above-mentioned reflective plate or layer as long as it can provide a specular surface. For example, silver, chrome, aluminum and stainless steel are eligible.
The plate-like substrate having a reflective layer and functioning as an electrode may be exemplified by the substrates exemplified with respect to the reflective electrode among which are self-supportive.
The ion conductive material layer to be disposed between the two conductive substrates is now described.
The ion conductive substance layer used in the present invention is composed of an ion conductive substance containing a specified electrochromic substance.
In the present invention, the term xe2x80x9cion conductive substancexe2x80x9d designates a substance having an ion conductivity of 1xc3x9710xe2x88x927S/cm or more at room temperature and playing a role of coloring, decoloring or discoloring an electrochromic substance. No particular limitation is imposed on the ion conductive material, which may thus be liquid, gel or solid. Solid ion conductive substances are particularly preferred for the purpose of the a invention because an electrochromic device which is overall solid and excelled in various performances for various practical usage can be obtained.
Liquid Ion Conductive Material
Eligible liquid ion conductive materials are those dissolving a supporting electrolyte such as salts, acids and alkalis in a solvent.
Although any suitable solvents may be used as long as they can dissolve a supporting electrolyte, preferred are those having polarity. Specific example of such solvents are water and an organic polar solvent such as methanol, ethanol, propylene carbonate, ethylene carbonate, dimethylsulfoxide, dimethoxyethane, acetonitrile, xcex3-butyrolactone, xcex3-valerolactone, sulforan, dimethylformamide, dimethoxyethane, tetrahydrofuran, propionnitrile, glutaronitlile, adiponitrile, methoxyacetonitrile, dimethylacetoamide, methylpyrrolidinone, dimethylsulfoxide, dioxolane, trimethylphosphate and polyethylene glycol. Preferred are propylene carbonate, ethylene carbonate, dimethylsulfoxide, dimethoxyethane, acetonitrile, xcex3-butyrolactone, sulforan, dioxolane, dimethylformamide, tetrahydrofuran, adiponitrile, methoxyacetonitrile, dimethylacetoamide., methylpyrrolidinone, dimethylsulfoxide, trimethylphosphate and polyethylene glycol. These may be used singlely or in combination.
Although not restricted, salts used as a supporting electrolyte may be alkali metal salts, inorganic ion salts such as alkaline earth metal salts, quaternary ammonium salts and cyclic quaternary ammonium salts. Specific examples of such salts include alkali metal salts of lithium, sodium or potassium such as LiClO4, LiSCN, LiBF4. LiAsF6, LiCF3SO3, LiPF6, LiI, Nal, NaSCN, NaClO4, NaBF4, NaAsF6, KSCN and KCl, quaternary ammonium salts or cyclic quaternary ammonium salts such as (CH3)4NBF4, (C2H5)4NBF4, (nxe2x80x94C4H9)4NBF4, (C2H5)4NBr, (C2H5)4NClO4 and (nxe2x80x94C4H9)4NClO4 and mixtures thereof
Acids used as a supporting electrolyte may be exemplified by inorganic acids and organic acids, specific examples of which include sulfuric acid, hydrochloric acid, phosphoric acid, sulfonic acid carboxylic acid.
Alkalis used as a supporting electrolyte include sodium hydroxide, potassium hydroxide and lithium hydroxide.
Gelatinized-liquid Ion Conductive Material
The gelatinized-liquid ion conductive material may be those which are gelatinized or made to be viscous by adding a polymer or a gelatinizer to the above-mentioned liquid ion conductive material.
No particular limitation is imposed on the polymers, which thus may be polyacrylonitrile, carboxymethylcellulose, polyvinyl chloride, polyethylene oxide, polyurethane, polyacrylate, polyamide, polyacrylamide, cellulose, polyester, polypropyleneoxide and nafion.
Preferred examples of the gelatinizers are oxyethylenemethacrylate, oxyethyleneacrylate, urethaneacrylate, acrylamide and agar-agar.
Solid Ion Conductive Material
No particular limitation is imposed on the solid ion conductive material as long as it is solid at room temperature and ion conductive. Preferred examples of such solid ion conductive materials are polyethyleneoxide, the polymer of oxyethylenemethacrylate, nafion, polystyrene sulfonate, Li3N, Na-xcex2-Al2O3 and Sn(HPO4)2H2O. Particularly preferred are polymer solid electrolytes obtained by polymerizing a polyethyleneoxide-based compound, an oxyalkyleneacrylate-based compound or a urethaneacrylate-based compound.
First examples of such polymer solid electrolytes are those obtained by solidifying a composition (hereinafter referred to as Composition A) containing the above-described organic polar solvent and supporting electrolyte and a urethaneacrylate of the formula (2) below.
The term xe2x80x9ccurexe2x80x9d used with respect to the polymer solid electrolyte as well as Composition B hereinafter described designates a state where a polymerizing or crosslinking component is cured with the progress of polymerization (polycondensation) or crosslinking and thus the composition does not flow at room-temperature. The composition thus cured has the basic structure in the form of network.
Formula (3) is represented by the formula 
wherein R6 and R7 may be the same or different and are each a group of formula (3), (4) or (5) below, R8 and R9 may be the same or different and are each a C1-C20, preferably C2-C12 divalent hydrocarbon residue, Y is selected from a polyether unit, a polyester unit, a polycarbonate unit and the mixed unit thereof and b is an integer from 1 to 100, preferably 1 to 50 and more preferably 1 to 20.
Formulae (3), (4) and (5) are represented by the formulae 
wherein R10, R11 and R12 may be the same or different and are each a hydrogen atom or a C1-C3 alkyl group and R13 is a C1-C20, preferably C2-C8 organic residue of divalent through quateivalent.
Specific examples of such organic residues are a hydrocarbon residue such as alkyltolyl, alkyltetratolyl and alkylene of the formula 
wherein R14 is a C1-C3 alkyl group or hydrogen, c is an integer from 0 to 6 and if c is 2 or greater, R14 groups may be the same or different.
The hydrocarbon residue may be a group part of which hydrogen atoms are substituted by an oxygen-containing hydrocarbon group such as a C1-C6, preferably C1-C3 alkoxy group and a C6-C12 aryloxy group.
Specific examples of R13 group in formulae (3) thorough (5) are those represented by the following formulae: 
Each of the divalent hydrocarbon residues represented by R8 and R9 in formula (2) is exemplified by a divalent chain-like hydrocarbon group, an aromatic hydrocarbon group and an alicyclic-containing hydrocarbon group. Specific examples of the chain-like divalent hydrocarbon group are those represented by formula (6) above.
Specific examples of the aromatic hydrocarbon group and alicyclic-containing hydrocarbon group are those represented by the following formulae: 
wherein R15 and R16 may be the same or different and each are a phenylene group, a phenylene group having an alkyl subsutituent, a cycloalkylene group and a cycloalkylene group having an alkyl substituent, R17, R13, R19 and R20 may be the same or different and each are a hydrogen atom or a C1-C3 alkyl group.
Specific examples of the groups R8 and R9 in formula (3) are those represented by the following formulae: 
In formula (2), xe2x80x9cYxe2x80x9d indicates a polyether unit, a polyester unit, a polycarbonate unit and mixed unit thereof. Each of these units is represented by the following formulae: 
In formulae (a) through (d), R21 through R26 may be the same or different and are each a C1-C20, preferably C2-C12 divalent hydrocarbon residue. Preferred for R24 are C2-C6 divalent hydrocarbon residues. Preferred for R21 through R26 are straight or branched alkylene groups among which methylene, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene and propylene groups are preferred for R23, and ethylene and propylene groups are preferred for R21, R22 and R24 through R26. The letter xe2x80x9cexe2x80x9d in formula (a) is an integer from 2 to 300, preferably 10 to 200, the letter xe2x80x9cfxe2x80x9d is an integer from 1 to 300, preferably 2 to 200, the letter xe2x80x9cgxe2x80x9d is an integer from 1 to 200, preferably 2 to 100, the letter xe2x80x9chxe2x80x9d is an integer from 1 to 200, preferably 2 to 100 and the letter xe2x80x9cixe2x80x9d is an integer from 1 to 300, preferably 10 to 200.
Each unit represented by formulae (a) through (d) may be a copolymer of the same or different units. Namely, if a plurality of R21 through R26 are present, the groups of each R21 thorough R26 may be the same or different. Preferred examples of the above-mentioned polymer are polymers of ethyleneoxide and propyleneoxide.
The urethaneacrylate may be prepared by any suitable conventional method. Urethaneacrylate of formula (3) has a molecular weight in the range from 2,500 to 30,000, preferably 3,000 to 20,000. The urethaneacrylate has preferably 2-6, more preferably 2-4 polymerization functional groups per molecule.
An organic polar solvent (organic nonaqueous solvent) is added in an amount of 100-200, preferably 200-900 weight parts per 100 parts of the urethaneacrylate. The addition of the organic polar solvent in a too less amount would result in insufficient ion conductivity, while the addition of the organic polar solvent in a too much amount would cause reduced mechanical strength. The supporting electrolyte may be salts, acids or alkalis. The supporting electrolyte should be added in an amount of 0.1 to 30, preferably 1 to 20 weight percent of the organic polar solvent.
Composition (A) is obtained by solidifying the above-described essential components, namely, urethaneacrylate, organic nonaqueous solvent and supporting electrolyte. If necessary, any suitable optional components may be added to Composition (A) as long as they are not obstructive to the achievement of the purpose of the invention. Such components may be crosslinkers and photo- or thermal polymerization initiators.
Second examples of the polymeric solid electrolyte are polymeric solid electrolytes obtained by solidifying a composition (hereinafter referred to as Composition (B)) comprising an organic polar solvent, a supporting electrolyte, a monofunctional acryloyle-modified polyalkylene oxide of formula (17) below or a polyfunctional acryloyle-modified polyalkylene oxide of formula (18) or (19) below.
Formula (17) is represented by the formula 
wherein R27, R28, R29 and R30 may be the same or different and are each hydrogen and an alkyl group having from 1 to 5 carbon atoms and j is an integer of 1 or greater Specific examples of the alkyl group include methyl, ethyl, i-propyl, n-propyl, n-butyl, t-butyl and n-pentyl. Preferred for R22, R23 and R34 are hydrogen and a methyl group. Preferred for R30 are hydrogen and methyl and ethyl groups.
The letter xe2x80x9cjxe2x80x9d in formula (17) is an integer of 1 or greater, usually from 1 to 100, preferably from 2 to 50 and more preferably from 2 to 30.
Specific examples of compounds represented by formula (17) are those having 1-100, preferably 2-50 and more preferably 1-20 oxyalkylene units, such as methoxypolyethylene glycol methacrylate, methoxypolypropylene glycol methacrylate, ethoxypolyethylene glycol methacrylate, ethoxypolypropylene glycol methacrylate, methoxypolyethylene glycol acrylate, methoxypolypropylene glycol acrylate, ethoxypolyethylene glycol acrylate, ethoxypolypropylene glycol acrylate and mixtures thereof.
If xe2x80x9cjxe2x80x9d is 2 or greater, the compound may be those having different oxyalkylene units, that is, copolymerized oxyalkylene units which for instance have 1-50, preferably 1-20 oxyethylene units and 1-50, preferably 1-20 oxypropylene units. Specific examples of such compounds are (ethylene.propylene) glycol methacrylate, ethoxypoly (ethylene.propylene) glycol methacrylate, methoxypoly (ethylene.propylene) glycol methacrylate, methoxypoly (ethylene.propylene) glycol acrylate, ethoxypoly methoxypoly (ethylene.propylene) glycol acrylate and mixtures thereof.
The polyfunctional acryloyl-modified polyalkylene oxide may be a bifunctional acryloyl-modified polyalkylene oxide represented by the formula 
wherein R31, R32, R33 and R34 are each hydrogen and a C1-C5 alkyl group and k is an integer of 1 or greater; or a polyfunctional acryloyl-modified polyalkylene oxide having more than three functional groups represented by the formula 
wherein R35, R36 and R37 are each hydrogen and a C1-C5) alkyl group, l is an integer of 1 or greater, m is an integer from 2 to 4 and L is a connecting group of valence indicated by m.
In formula (18), R31, R32, R33 and R34 are each hydrogen or a C1-C5 alkyl group, such as methyl, ethyl, i-propyl, n-propyl, n-butyl, t-butyl, t-butyl and n-pentyl among which preferred are hydrogen and particularly preferred is methyl.
The letter xe2x80x9ckxe2x80x9d in formula (18) is an integer of 1 or greater, usually from 1 to 100, preferably from 2 to 50, more preferably from 2 to 30. Preferred examples of compounds of formula (19) are those having 1-100, preferably 2-50, more preferably 1-20 oxyalkylene units such as polyethylene glycol diacrylate, polypropylene glycol dimethacrylate, polyethylene glycol diacrylate, polypropylene glycol dimethacrylate and mixtures thereof.
If k is 2 or greater, the compounds of formula (18) may be those having different oxyalkylene units, that is, polymerized oxyalkylene unit having 1-50, preferably 1-20 oxyethylene units and 1-50, preferably 1-20 oxypropylene units, such as poly(ethylene.propylene)glycol dimethacrylate, poly(ethylene.propylene)glycol diacrylate and mixtures thereof.
In formula (19), R35, R36 and R37 are each hydrogen or a C1-C5 alkyl group, such as methyl, ethyl, i-propyl, n-propyl, n-butyl, t-butyl and n-pentyl. Particularly preferred for R35, R36 and R37 are hydrogen and a methyl group.
The letter xe2x80x9clxe2x80x9d is an integer of 1 or greater, usually from 1 to 100, preferably from 2 to 50 and more preferably from 2 to 30.
The letter xe2x80x9cmxe2x80x9d indicates the number of connecting group xe2x80x9cLxe2x80x9d and is an integer from 2 to 4.
Connecting group xe2x80x9cLxe2x80x9d is a divalent, trivalent or quatravalent hydrocarbon group having 1-30, preferably 1-20 carbon atoms.
Such divalent hydrocarbon groups may be alkylene, arylene, arylalkylene, alkylarylene and hydrocarbon groups having those groups as the base skeleton. Specific examples of such hydrocarbon groups are those represented by the following formulae 
Such trivalent hydrocarbon groups may be alkyltryl, aryltryl, arylalkyltryl, alkylaryltryl and hydrocarbon groups having those groups as the base skeleton. Specific examples of such hydrocarbon groups are those represented by the following formulae: 
Such quatravalent hydrocarbon groups may be alkyltetraryl, aryltetraryl, arylalkyltetraryl, alkylaryltetraryl and hydrocarbon groups having those groups as the base skeleton. Specific examples of such hydrocarbon groups are those represented by the following formulae: 
Specific examples of compounds of formula (20) are those having 1-100, preferably 2-50, more preferably 1-20 of an oxyalkylene units such as trimethylolpropanetri(polyethylene glycol acrylate), trimethylolpropanetri(polyethylene glycol methaacrylate), trimethylolpropanetri(polypropylene glycol acrylate), trimethylolpropanetri(polypropylene glycol methaacrylate), tetramethylolmethanetetra(polyethylene glycol acrylate), tetramethylolmethanetetra(polyethylene glycol methaacrylate) tetramethylolmethanetetra(polypropylene glycol acrylate), tetramethylolmethanetetra(polypropylene glycol methaacrylate), 2,2-bis[4-(acryloxypolyethoxy)phenyl]propane, 2,2-bis[4-(methaacryloxypolyethoxy)phenyl]propane, 2,2-bis[4-(acryloxypolyisopropoxy)phenyl]propane, 2,2-bis[4-(methaacryloxypolyisopropoxy)phenyl]propane and mixtures thereof.
If l is 2 or greater, compounds of formula (20) may be those having different oxyalkylene units, that is, polymerized oxyalkylene units having 1-50, preferably 1-20 of oxyethylene units and 1-50, preferably 1-20 oxypropylene units. Specific examples of such compounds include trimethyloipropaneti(poly(ethylene.propylene)glycol acrylate), trimethylolpropanetri(poly(ethylene.propylene)glycol methaacrylate), tetramethylolmethanetetra(poly(ethylene.propylene)glycol acrylate), tetramethylolmethanetetra(poly(ethylene.propylene)glycol acrylate) and mixtures thereof.
There may be used the difunctional acryloyl-modified polyalkyleneoxide of formula (18) and the polyfunctional acryloyl-modified polyalkyleneoxide of formula (19) in combination. When these compounds are used in combination, the weight ratio of the compound of formula (18) to that of formula (19) is in the range from 0.01/99.9 to 99.9/0.01, preferably from 1/99 to 99/1 and more preferably from 20/80 to 80/20.
The above-described organic polar solvent should be added in an amount of 50-800, preferably 100-500 weight percent based on the weight of the polyfunctional acryloyl-modified polyalkyleneoxide. The above-described supporting electrolyte should be added in an amount of 1-30, preferably 3-20 weight percent based on the total weight of the polyfunctional acryloyl-modified polyalkyleneoxide and the organic polar solvent.
Similarly to Composition (A), if necessary, cross-linkers or polymerization initiators may be added to Composition (B). Such components should be added in an amount of 0.005-5, preferably 0.01-3 weight percent based on the total weight of the polyfunctional acryloyl-modified polyalkylene oxide.
In the present invention, regardless of whether the ion conductive substance is liquid, gelatinized liquid or solid, an ion conductive substance layer is formed using a dispersion obtained by dispersing a specified electrochromic substance into the ion conductive substance.
An electrochromic substance which is a requisite component in the present invention and is dispersed into the ion conductive substance, typically the above-described Compositions (A) or (B), is a compound represented by the formula 
wherein Xxe2x88x92 and Yxe2x88x92 are each a counter anion and may be the same or different and an anion selected from the group consisting of a halogen anion, ClO4xe2x88x92, BF4xe2x88x92, PF4xe2x88x92, CH3COOxe2x88x92 and CH3(C5H4)SO3xe2x88x92 and R1 and R2 may be the same or different and are each a hydrocarbon group having from 1 to 20 carbon atoms.
The halogen anion may be Fxe2x88x92, Clxe2x88x92, Brxe2x88x92 and Ixe2x88x92. In formula (1), R1 and R2 are each independently a hydrocarbon group having from 1 to 20, preferably 1 to 12 carbon atoms and may be the same or different. Specific examples of the hydrocarbon group are an alkyl group, an aralkyl group or an aryl group, and preferably an alkyl group and aralkyl group. Specific examples of such an alkyl group are methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl and n-hexyl groups. Specific examples of such an aralkyl group are benzyl,phenetyl, phenylpropyl, trimethyl and ethylphenylmethyl groups.
Specific examples of a compound having a viologen structure of formula (1) are N,Nxe2x80x2-diheptylbipyiidiniumdibromide,
N,Nxe2x80x2-diheptylbipyridiniumdichloride,
N,Nxe2x80x2-diheptylbipyridiniumdiperchlorate,
N,Nxe2x80x2- diheptylbipyridiniumtetraphloroborate,
N,Nxe2x80x2-diheptylbipyridiniumhexaphlorophosphate,
N,Nxe2x80x2-dihexylbipyridiniumdibromide, N,Nxe2x80x2-dihexylbipyridiniumdichloride,
N,Nxe2x80x2-dihexylbipyridiniumdiperchlorate,
N,Nxe2x80x2- dihexylbipyridiniumtetraphloroborate,
N,Nxe2x80x2- dihexylbipyridiniumdihexaphlorophosph ate,
N,Nxe2x80x2-dipropylbipyridiniumdibromide, N,Nxe2x80x2-dipropylbipyridiniumdichloride,
N,Nxe2x80x2-dipropylbipylidiniumdiperchlorate,
N,Nxe2x80x2- dipropylbipyridiniumtetraphloroborate,
N,Nxe2x80x2-dipropylbipyrndiniumdihexaphlorophosphate,
N,Nxe2x80x2-dibenzylbipynidiniumdibromide,
N,Nxe2x80x2-dibenzylbipyridiniumperchlorate,
N,Nxe2x80x2-dibenzylbipyridiniumtetraphloroborate,
N,Nxe2x80x2- dibenzylbipyiidiniumdihexaphlorophosphate,
N-heptyl-Nxe2x80x2-benzylbipryridiniumdiperchlorate,
N-heptyl-Nxe2x80x2-benzylbipryridiniumditetraphloroborate,
N-heptyl-Nxe2x80x2-benzylbipryridinumdibromide,
N-heptyl-Nxe2x80x2-benzylbipryidiniumdichloride,
N-heptyl-Nxe2x80x2-methylpyridiniumdibromide and
N-heptyl-Nxe2x80x2-methylpyridiniumdichloride.
Although the concentration of an electrochromic substance of formula (1) in an ion conductive substance layer is arbitrarily selected. However, it is within the range of from 0.00001 to 50 percent by weight, preferably 0.0001 to 30 percent by weight and more preferably 0.001 to 10 percent by weight.
If necessary, an electrochromic substance of formula (1) may be doped with a compound facilitating coloration. Alternatively, an electrochromic substance and an electron donating compound may coexist in an ion conductive substance layer.
The ion conductive substance layer of the electrochromic device according to the present invention is formed from an ion conductive substance containing an electrochromic substance of formula (1) dispersed therein.
Any suitable method can be employed for forming the ion conductive substance layer. When a liquid or gelatinized liquid ion conductive substance is used, the ion conductive substance containing an electrochromic substance dispersed therein is injected into the space provided between two electrically conductive substrates, i.e. counter conductive substrates, placed, facing each other and then sealed at the edges of the opposed surfaces, by vacuum injection, atmospheric injection or a meniscus method. Alternatively, when using a specific type of ion conductive substance, a method can be employed in which an ion conductive substance layer containing an electrochromic substance is formed on one of the electrically conductive substrates by sputtering, evaporation or a sol-gel method and the substrate is put together with the other substrate. Further alternatively, an electrochromic device according to the present invention can be obtained by inserting a film-like ion conductive substance containing an electrochromic substance between a pair of glasses to form a laminated glass.
When a solid ion conductive substance, particularly the above-described Composition A or B is used, a method can be employed in which the composition in an unsolidified state is inserted into the space between the counter conductive substrates with their peripheral edges being sealed, by vacuum injection, atmospheric injection or a meniscus method and is cured in a suitable manner.